Primates: Filogenia e historia biogeográfica

Abstract

Numerous recent works (paleontology, anatomy, biochemistry, paleobiogeography) allow to give a sketch of the history of the Primates, and to discuss their origin, comprehension, phylogeny and classification. The limits of the orden have been made more precise; the only remaining problem is that of the Microsyopidae, to which is linked ultimately the possibility of a diagnosis of the group. According to CLEMENS, Purgatorius is indeed a Primate, related to the Paromomyidae, and probably derived from the Erinaceomorpha. But it would be rash to place it at the origin of all Primates and to locate their cradle in North America. It is the forerunner and perhaps the ancestor of the Plesiadapiformes, which enjoyed a noticeable adaptive radiation, limited however in time (late Cretaceous-Eocene) and space (North America and Europe: but Azibius, from the Eocene of the Sahara, might suggest an extension to Africa). Other Primates split at an early date into Strepsirhini and Haplorhini, a dichotomy confirmed by GOODMAN (biochemistry) and LUCKETT (placentation), but rejected by GINGERICH (whose phylogeny is based essentially on dental characters). The well delineated Strepsirhini ( = Lemuriformes s.l.) have raised phylogenic problems which are now somewhat clearer. Originating probably in Africa (although no early fossils are known there, for lack of suitable fossiliferous localities), they invaded Laurasia at the beginning of the Eocene, with the Adapoidea, which spread widely, but became extinct early in the Oligocène, at least in North America and Europe. Another migration reached Madagascar (during the Eocene?), where it gave rise to a remarkable radiation: Lemuroidea (to which the Cheirogaleidae should be restored) and Daubentonioidea (which have split off early, despite contrary opinions). In Africa, the Lorisoidea (closer to the Lemuroidea than was believed) are unknown before the Miocene, and then reach Southern Asia. The Haplorhini split into two groups, Tarsiiformes and Simiiformes, which have differentiated through geographical segregation North and South of the Tethys. The exclusively Laurasian Tarsiiformes have enjoyed considerable success in the Paleogene, but Neogene fossils (expectable in Asia) are all but unknown. The recent Tarsius, probably driven into the islands of South-East Asia by the invasion of the African Primates, is still much isolated. The Simiiformes, initially restricted to southern lands, probably originated in Africa where the Oligocène monkeys from the Fayum must have their ancestors (unknown, however, for lack of fossiliferous localities). The Atlantic must have been crossed by an early offshoot, the Platyrrhini, whose African origin in increasingly well supported (while other hypotheses remain fragile); they colonized South America as early as the Oligocène, and have then reached the West Indies (by sea), and still later Central America (through Panama). In Africa, the Catarrhini have differentiated into six families (one of which short-lived); some of them have succeeded in living outside the forest; from the Miocene onward, a reestablished land connection has allowed the five then living; families (among which the Hominidae) to enter Eurasia, some of them spreading out widely there. The Primates provide us with paleogeographical data: a connection between North America and Europe until the early Eocene; then isolation (endemism) of Western Europe until the "Grande Coupure"; a connection between Africa and Eurasia before the Eocene and after the Oligocène. But they were able to cross some seas: colonization of Madagascar and South America from Africa. Geographical segregation has played an essential part in their differentiation: Plesiadapiformes in North America; Adapinae and Microchoerinae in Europe; Lemuroidea and Daubentonioidea in Madagascar; Tarsiiformes in Laurasia; Catarrhini in Africa and Platyrrhini in South America. Obviously, as for many other groups, their evolution has involved not only genetic and ecological factors, but also geographical ones.